On another forum, they added up the various calculable error-factors which are all highly sensitive at this range, the logistical impracticality (first of finding the guy at such range, and second of choosing to use a rifle vs. some other method like airstrike or artillery), and the known limitations of the equipment referenced as far as elevation adjustment capability and intrinsic platform accuracy. In short, there's no way this shot happened, unless by pure accident, which would in turn be the least likely thing that has ever happened. A claim like this seems plausible since shots well beyond 1000yrds are now common and we lose perspective when the number is so large, but closer examination suggests it is grossly exaggerated at best. It's like claiming that tool-bag they accidentally lost on the International Space Station a while back landed on a fighter's head on purpose. To pull this off as described, the shooter would need exact, not estimated, data for weather across the entire flight path, lattitude, distance, elevation, some object a known distance far above the target to 'Kentucky Windage' off of when the scope runs out of adjustment, eyes that can pick out a grain of sand through even a high-magnification telescopic sight, and even then you're still stuck with a human target that will typically move before the 8 second transit time (weather, too), and a 50BMG platform that is generally in the 1-2MOA range on a good day as opposed to the ~.05MOA accuracy needed for this shot. No mention in the story of the (likely dozens) of shot attempts needed to finally pull this off in reality, that could be delivered far more effectively at such extreme range by an M2HB.
That new remote-controlled 50cal bullet DARPA's working on could have maybe done it under test conditions, but that wasn't mentioned either.
Stories like this one seem to come up every few months, usually at ever-longer distances (an increase of like 50% this time, despite all the top-flight snipers in operation across the world today trying to outdo each other) and usually involving some kind of Hollywood-style plot element, like a guy about to kill a victim getting killed just in the nick of time. Makes for entertaining reading, but in reality a dime-novel fantasy; "Daring Tales of Hero Snipers"
TCB